This invention relates to a trailer coupling that will receive both a spherical cavity coupler and a drawbar eye.
There are two types of trailer couplings that are commonly used. For light loads a spherical cavity coupler is placed on a spherical ball. With heavier loads an annular drawbar eye is placed on a cylindrical pintle. The use of these two types of trailer couplings is not mutually exclusive, however, and in some applications it is desirable to accommodate both types of coupler elements on the same vehicle. While it is possible to place two trailer couplings on a vehicle, doing so is expensive and inconvenient.
Thelin, U.S. Pat. No. 3,963,266 attempts to overcome this problem with a duplex trailer coupling that accommodated both types of coupler elements. There are two difficulties with Thelin, however, which makes it less than an ideal solution to this problem. First Thelin places the drawbar eye around the spherical ball that carries the spherical cavity coupler. This creates point loading which causes excessive wear on both the drawbar eye and the ball. Secondly, the latch used by Thelin to prevent the drawbar eye from being displaced from the trailer coupling pivots about a horizontal axis. Thus the latch has to be raised to displace it from the ball in order to install or remove the drawbar eye or to use the trailer coupling with a spherical cavity coupler. In many applications there is not sufficient room to accommodate a trailer coupling of this type. Furthermore, when the device is used on a pickup truck, lowering the tailgate when the latch is in its raised position will cause the tailgate to hit the latch, potentially causing damage to both the latch and the tailgate. In addition, while the latch in Thelin prevents the drawbar eye from being displaced from the coupling element it does not prevent it from moving up and down relative to the ball. Since the ball is sized to snugly receive the drawbar eye, as the eye raises or lowers on the ball excessive clearance is created which causes excessive wear, and may create shock loading that could shatter the ball or eye.
The subject invention overcomes the foregoing problems with the prior art by providing a trailer coupling having a body that is attachable to a flat surface at the back of a towing vehicle. An arm located at the lower portion of the body projects rearwardly from the vehicle and has a coupler-receiving element attached to it. Preferably the coupler-receiving element is removably attached to the arm, and in a preferred embodiment this is accomplished by placing a threaded stud at the bottom of the coupler element through a hole in the arm and installing a nut on the stud. The upper portion of the coupler element is a spherical ball which is configured to receive a standard spherical cavity coupler. A cylindrical neck, which is configured to receive a standard drawbar eye, extends between the ball and the arm.
A latch, which is attached to the body, pivots about a vertical axis between a closed position where it contacts the coupler element and an open position where it is displaced from the coupler element. When the latch is in its open position the ball is exposed and the trailer coupling can be used with a spherical cavity coupler. Also when the latch is in its open position a drawbar eye can be placed on the coupler-receiving element. Once the drawbar eye is in place on the coupler-receiving element, the latch is moved to its closed position to prevent the drawbar eye from becoming displaced. The latch also holds the drawbar eye down on the neck where there is a large contact area, and wear is reduced.
In a preferred embodiment of the invention, the latch includes a locking element which positively locks the latch in its closed position and prevents free rotation of the latch out of its open position. The locking element is released by raising a trigger that is accessible through a finger-receiving cavity in the latch.
Accordingly, it is a principal object of the subject invention to provide a trailer coupling that receives both a spherical cavity coupler and a drawbar eye.
It is a further object of the subject invention to provide such a trailer coupling having a latch, that prevents inadvertent removal of the drawbar eye, which moves between its open and closed position by pivoting about a vertical axis.
It is a still further object of the subject invention to provide such a trailer coupling having a locking mechanism associated with the latch which positively locks the latch in its closed position and holds it from inadvertently being rotated out of its open position.
It is a further object of the subject invention to provide such a trailer coupling that utilizes a finger-operated trigger to release the locking mechanism when the latch is in its closed position.
It is a yet further object of the subject invention to provide such a trailer coupling in which the latch mechanism never needs to be raised substantially above the top of the ball that receives the spherical cavity coupler.
It is a yet further object of the subject invention to provide such a trailer coupling that has a replaceable coupler-receiving element that receives both the spherical cavity coupler and the drawbar eye.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.